A gambling addict is suing a British betting chain after he lost millions of dollars on bets, despite asking to have his account closed, his lawyers said Wednesday.

Graham Calvert, a 28-year-old greyhound trainer, twice asked William Hill PLC to stop accepting his bets, but he was nonetheless allowed to gamble 3.5 million pounds ($6.9 million) over a six-month period in 2006, his law firm, Ward Hadaway, said in a statement.

Calvert lost a total of 2.1 million pounds ($4.1 million), including 347,000 pounds ($680,000) when he bet the United States would win the 2006 Ryder Cup. His gambling addiction cost him his training license, his business, and his marriage, Ward Hadaway said.

Calvert told the British Broadcasting Corp. television he blamed William Hill for letting him lose the money.

"If I'd known I had the problem and didn't do anything about it, then I would see myself as being 100 percent responsible," he told BBC television. "But the fact (is) that I did try, did go through the right procedures."

Peter Hornsey, one of Calvert's lawyers, said the case was a crucial test of the betting industry's so-called "self-exclusion" policies, whereby betters can ask operators to block them from gambling for a minimum period of six months.

"It goes to the issue of how bookmakers treat people who have gambling problems via their self-exclusion policy," Hornsey said in the statement.

"For whatever reason, William Hill failed to operate its self-exclusion policy, with disastrous consequences for our client despite knowing that he had a gambling problem and we argue that they should be held responsible for that," the statement said.

William Hill, which runs more than 2,000 betting shops across Britain, said only that they would be contesting the case vigorously, declining to go into details.

The betting chain is one of the biggest players in the country's 91.5 billion-pound ($179.3 billion) gambling industry. According to the Responsibility in Gambling Trust, which funds research into responsible gambling, all operators must have a way to allow their customers to "self-exclude."

Calvert's case is due to be heard at the High Court in London on Monday, his lawyers said.

More information on the negative effects of gambling.